Commonly-owned U.S. patent application Ser. No. 08/152,812 filed 16 Nov. 93 (now U.S. Pat. No. 4,576,211, issued 19 Dec. 95), and its counterpart commonly-owned “divisional” U.S. patent applications Ser. Nos. 08/457,479 filed 01 Jun. 95 (now U.S. Pat. No. 6,049,976) and 08/570,230 filed 11 Dec. 95 (now U.S. Pat. No. 5,852,871), all by KHANDROS, disclose methods for making resilient interconnection elements for microelectronics applications involving mounting an end of a flexible elongate core element (e.g., wire “stem” or “skeleton”) to a terminal on an electronic component coating the flexible core element and adjacent surface of the terminal with a “shell” of one or more materials having a predetermined combination of thickness, yield strength and elastic modulus to ensure predetermined force-to-deflection characteristics of the resulting spring contacts. Exemplary materials for the core element include gold. Exemplary materials for the coating include nickel and its alloys. The resulting spring contact element is suitably used to effect pressure, or demountable, connections between two or more electronic components, including semiconductor devices.
Commonly-owned, U.S. Pat. No. 5.917,707 and its corresponding PCT Patent Application No. PCT/US94/13373 filed 16 Nov. 94 (WO95/14314, -published 26 May 95) [underlining from original deleted from previous part], both by KHANDROS and MATHIEU, disclose a number of applications for the aforementioned spring contact element, and also disclosed techniques for fabricating contact pads at the ends of the spring contact elements. For example, in FIG. 14 thereof, a plurality of negative projections or holes, which may be in the form of inverted pyramids ending in apexes, are formed in the surface of a sacrificial layer (substrate). These holes are then filled with a contact structure comprising layers of material such as gold or rhodium and nickel. A flexible elongate element is mounted to the resulting contact structure and can be overcoated in the manner described hereinabove. In a final step, the sacrificial substrate is removed. The resulting spring contact has a contact pad having controlled geometry (e.g. , sharp points) at its free end.
Commonly-owned, U.S. patent application Ser. No. 08/452,255 filed 26 May 95 and, now U.S. Pat. No. 6,336,269, its corresponding PCT Patent Application No. PCT/US95/14909 filed 13 Nov. 9 (WO96/17278, -published 06 Jun. 96), both by ELDRIDGE, GRUBE, KHANDROS and MATHIEU, disclose additional techniques and metallurgies for fabricating contact tip structures on sacrificial substrates, as well as techniques for transferring a plurality of spring contact elements mounted thereto, en masse, to terminals of an electronic component (see, e.g., FIGS. 11A-11F and 12A-12C therein).
Commonly-owned, copending U.S. Provisional Patent Application No. 60/024,555 filed 26 Aug. 1996, by ELDRIDGE, KHANDROS and MATHIEU, discloses, for example at FIGS. 2A-2C thereof, a technique whereby a plurality of elongate tip structures having different lengths than one another can be arranged so that their outer ends are disposed at a greater pitch than their inner ends. Their inner, “contact” ends may be collinear with one another, for effecting connections to electronic components having terminals disposed along a line, such as a centerline of the component.
The present invention addresses and is particularly well-suited to making interconnections to modern microelectronic devices having their terminals (bond pads) disposed at a fine-pitch. As used herein, the term “fine-pitch” refers to microelectronic devices that have their terminals disposed at a spacing of less than 5 mils, such as 2.5 mils or 65 μm. As will be evident from the description that follows, this is preferably achieved by taking advantage of the close tolerances that readily can be realized by using lithographic rather than mechanical techniques to fabricate the contact elements.